Cathode ray tubes are increasingly being used as visual display terminals (VDT's) which are scanned at close range by the human eye. It is desirable to minimize the glare that is reflected from the glass surface of the CRT so as to enable the user to more easily read the graphics and other display characters that are shown on the screen.
Various methods are known for reducing the glare on CRT face panels. U.S. Pat. No. 4,945,282 to Kawamura describes a process for providing antistatic and antiglare properties to the surface of a CRT. The process involves applying a suspension of electroconductive metal oxide particles in an alcoholic solution of alkoxysilane onto the front surface of a CRT. This is followed by heat treatment to the resulting coat to form an antistatic film comprising a transparent electroconductive SiO.sub.2 coat on the front surface. Antiglare properties are provided by applying a second non-glare film over the electroconductive SiO.sub.2 coat. The formulation of the non-glare film includes the steps of dispersing fine SiO.sub.2 particles in an alcoholic solution of alkoxysilane, applying the suspension over the antistatic film which is the transparent substrate formed on the panel and heating the resultant coat to decompose the alkoxysilane to form a thin SiO.sub.2 film to thereby cover and fix the fine SiO.sub.2 particles.
U.S. Pat. No. 4,563,612 to Deal, et al. describes a cathode ray tube having an antistatic, glarereducing coating. The coating has a rough surface which is composed essentially of a silicate material and an inorganic metallic compound. The coating is applied by spraying a solution of a water soluble salt of one or more of a metal selected from platinum, tin, palladium and gold in a lithium stabilized silica sol onto the surface of the cathode ray tube. A solution of lithium, sodium and potassium silicate or an organic silicate, such as tetraethyl orthosilicate may be substituted for the lithium stabilized silica sol.
U.S. Pat. No. 4,582,761 to Liu discloses an aqueous dispersion of polyvinyl acetate for use as a coating on an electronic viewing screen to provide antiglare properties.
U.S Pat. No. 3,689,312 to Long, et al. is directed to a method for producing a glare-reducing coating on the surface of a cathode ray tube. The method includes the steps of preparing a coating formulation consisting of a solution of a siliceous polymer and an organic polymer in a volatile organic liquid vehicle for the polymers. The solution is then sprayed onto the surface of a cathode ray tube to coat the surface. The cathode ray tube is then baked at a temperature of 100.degree. C to 200.degree. C. to cure the coating.
A cathode ray tube having an antistatic film is disclosed in U.S. Pat. No. 4,785,227 to Matsuda, et al. The antistatic film is applied by dipping the cathode ray tube into a mixture of tetraethyl silicate, propanol and butanol containing a colloidal solution of metal particles.
It is known to apply a solution of tetrachlorosilane in an anhydrous alcohol to the surface of a CRT heated to 50.degree. C. to 80.degree. C. to reduce glare. The tube surface is then heated to a temperature up to 200.degree. C. for 15-20 minutes to cause polymerization of the silane to a polysiloxane. In this method, the silane solution is sprayed onto the surface of the CRT in the form of discrete island droplets of the solution. A continuous film of the solution must be avoided to provide optimum antiglare properties.
It is also known to apply coatings of lithium silicate onto the surface of a CRT to provide antiglare properties.
While various prior art methods have been proposed for reducing gloss and providing antiglare properties to the surface of a CRT, such methods have not met with complete success. It is important that any coating provided on the surface of the CRT to reduce gloss does not impart undesirable side effects, such as the provision of a mottled or uneven surface. The diffusive reflectivity of the surface imparted by the coating should also not be substantially different than that of the uncoated CRT.